Brass type musical wind instruments typically utilise several metal tubing lengths in order to provide tone intervals in conjunction with harmonics, whereby flow of air from the mouthpiece end to the bell pipe end of the instrument is routed by a player via different air passage ways due to combinations of different tubing, such that an appropriate pitch or tone range is provided.
In order to route passage of air through the instrument, a player-operable valve arrangement is provided, whereby movement of one or more valves routes air flow through some air passage ways whilst occluding others, so as to provide the requisite air passage way length for a desired musical note. Such valves are comprised of a moveable valve member which is movable relative to a valve housing in which it is contained.
Traditionally brass instruments use linear valves as a valve piston which move in a linear direction within a cylindrical sleeve or valve housing responsive to a linear force from a player's finger movement. The valve piston is then returned to an initial state by way of a return spring. Such linear valves are typically utilised in trumpets, tenor horns, tubas, euphoniums and the like.
In some other brass instruments, rotary valves may be used such as are utilised in a French horn, and are operable by key members, to move the valve body in a rotary direction within a circular sleeve or valve housing, similarly as to vary the length of the air passage way within the tubular body of the instrument during play and thereby change the pitch of the instrument.
Such linear and rotary valves tend to require a relatively high degree of precision to manufacture including machining of the curved metal surface of the valve piston or valve rotor (valve element) to ensure that openings of air passage ways located in and extending through the curved surface of the cylindrical valve body are able to align precisely with corresponding openings in the housing when the valve is rotated so as to appropriately re-direct air flow through different air-flow passage ways within the tubular body. Precision machining of such linear and rotary valves is also required to prevent air escaping from between the contact formed by the curved inner surface of the valve housing and the curved outer surface of the valve element, which causes significant loss in sound energy and quality
A common frustration to instrument players is sticky or lagging valves, which due to alignment, wear, precision of fit, insufficient lubricant, can cause incomplete, delayed or gradual occlusion and opening of air passage ways, causing interruption of playing of an instrument by a player. Often, heavy return springs are used to return the moveable valve element to its initial position, and such biasing force is required to be overcome in order to move the valve, which can particularly be difficult for young players to operate.
Poor intonation provided by some brass instruments (that is, the pitch between notes) is another frustration to players, and often exists in lower-end cost instruments. Reasons for poor intonation can include inaccurate tube lengths for various portions of a brass instrument such a both fixed length and optionally slidable members, as well as connecting tubes between valves, and small changes in length or inaccuracy in manufacture can affect the intonation of a brass instrument.